The present invention is directed to electrochemical cells generally known as button cells, and to a method of sealing such cells. More particularly, the present invention is directed to a double sealable button cell with a corrosion resistant can, and to a method of double sealing the can.
The need for button type electrochemical cells has mushroomed with the advent of the electric watch and other electronic devices. As a result, the recent prior art is replete with button cell configurations to serve particular needs. For example, U.S. Pat. No. 4,021,598, Naruishi et al, illustrates one type of conventional button cell having a conductive can and a conductive cover with an insulative gasket therebetween, with sealing achieved by crimping the upper portion of the can wall over gasket and cover. While such cells are satisfactory for some types of electrochemical components, the need for better sealing developed for certain corrosive or leakable electrochemical components. Thus, for example, U.S. Pat. Nos. 4,015,056 (Megahed et al) and 4,009,0456 (Megahed et al) show one approach to further leakage prevention, i.e., the use of the double top. U.S. Pat. Nos. 4,015,055 (Langan et al) and 4,008,357 (Nishimura et al) show the use of a U-shape flange top for enhanced crimping seal. In complicated metal/air and metal/oxygen cells where subassembly components and predetermined gas spaces are required multiple sealing techniques have been applied. Thus, for example, in U.S. Pat. No. 3,746,580 (Aker et al) a gas depolarizable metal/air cell is described which has an insert molded cathode subassembly with non-conductive plastic portions which are sealed, e.g., by heat or ultrasons, to an anode assembly at certain of its non-conductive plastic portions. The resulting assemblage is further sealed in a crimped can fashion.
Not only have enhanced sealing means been developed to prevent leakage, but leakage by corrosion of metallic parts has been a problem when certain electrochemical components are used. Thus, for example, U.S. Pat. Nos. 3,756,856 (Tennenhouse) and 2,812,377 (Franquemont) disclose the use of conductive carbon plastic coatings to render cell metal parts corrosion resistant yet conductive.
Notwithstanding all of the foregoing teachings of the prior art, it is believed that the unique button cell of the present invention has not heretofore been taught nor rendered obvious.